U.S. Pat. No. 4,806,893 entitled "Molded Case Circuit Breaker Actuator-Accessory Unit" describes the use of an electromagnetic actuator within an actuator-accessory unit to articulate a circuit breaker operating mechanism to separate the circuit breaker contacts upon the occurrence of an overcurrent condition of predetermined magnitude. An electronic trip unit in combination with current transformers are used within so-called "electronic trip" circuit breakers to sense the circuit current and determine when such a tripping function should be inputted to the actuator-accessory unit. The electronic trip unit and actuator-accessory unit replace prior art thermally and magnetically active trip elements which respond to changing circuit current in an analog fashion.
The operating mechanism and latch assembly used within the electronic trip circuit breakers are described in U.S. Pat. No. 4,736,174 entitled "Molded Case Circuit Breaker Operating Mechanism" and U.S. Pat. No. 4,864,263 entitled "Molded Case Circuit Breaker Latch and Operating Mechanism Assembly".
The "tripping force" for purposes of this disclosure is defined as the amount of force required to displace the operating mechanism latch from the operating cradle to allow the operating springs to overcenter and separate the circuit breaker contacts.
With higher ampere-rated circuit breakers, a higher tripping force is generally required to overcome the higher latching forces generated between the operating cradle and the latch assembly. U.S. patent application Ser. No. 518,673 filed May 3, 1990 and entitled "Tripping Arrangement for Molded Case Circuit Interrupter" describes a supplemental tripping assembly for providing additional trip force to one such higher ampere-rated industrial circuit breaker. Another approach to compensate for the higher trip forces required with higher ampere-rated industrial circuit breakers is to provide a supplemental latch in combination with the latch assembly which effectively reduces the latching forces. One such supplemental latch is found within U.S. patent application Ser. No. 526,481 filed May 21, 1990 and entitled "Molded Case Circuit Breaker Compact Latch Assembly". All of the aforementioned U.S. Patents and Patent Applications are incorporated herein for reference purposes.
It would be economically advantageous to reduce the tripping force in molded case circuit breakers without requiring a supplemental tripping mechanism or supplemental latch assembly. Accordingly, one purpose of the instant invention is to provide an operating cradle configuration that requires a reduced tripping force to displace the operating cradle from the circuit breaker latch assembly.